From 517d3bb4dd17e9c51690c98d747b86a0ed8b2fbf Mon Sep 17 00:00:00 2001 From: Juan Alvarez Date: Tue, 15 Aug 2023 16:53:30 -0300 Subject: [PATCH] Fixed #34779 -- Avoided unnecessary selection of non-nullable m2m fields without natural keys during serialization. By using `select_related(None)` instead of `select_related()`, the unnecessary joins are completely avoided. Note that the current tests already covers the change, when the field is not `null=True`. Regression in f9936deed1ff13b20e18bd9ca2b0750b52706b6c. --- django/core/serializers/python.py | 5 ++++- django/core/serializers/xml_serializer.py | 5 ++++- docs/releases/4.2.5.txt | 4 ++++ tests/serializers/models/base.py | 2 +- 4 files changed, 13 insertions(+), 3 deletions(-) diff --git a/django/core/serializers/python.py b/django/core/serializers/python.py index 0dc504aa34e..7ec894aa00a 100644 --- a/django/core/serializers/python.py +++ b/django/core/serializers/python.py @@ -80,7 +80,10 @@ class Serializer(base.Serializer): def queryset_iterator(obj, field): return ( - getattr(obj, field.name).select_related().only("pk").iterator() + getattr(obj, field.name) + .select_related(None) + .only("pk") + .iterator() ) m2m_iter = getattr(obj, "_prefetched_objects_cache", {}).get( diff --git a/django/core/serializers/xml_serializer.py b/django/core/serializers/xml_serializer.py index e0129a59bb8..3f9955aa23c 100644 --- a/django/core/serializers/xml_serializer.py +++ b/django/core/serializers/xml_serializer.py @@ -156,7 +156,10 @@ class Serializer(base.Serializer): def queryset_iterator(obj, field): return ( - getattr(obj, field.name).select_related().only("pk").iterator() + getattr(obj, field.name) + .select_related(None) + .only("pk") + .iterator() ) m2m_iter = getattr(obj, "_prefetched_objects_cache", {}).get( diff --git a/docs/releases/4.2.5.txt b/docs/releases/4.2.5.txt index 480b21d9028..96b32d6dfc3 100644 --- a/docs/releases/4.2.5.txt +++ b/docs/releases/4.2.5.txt @@ -16,3 +16,7 @@ Bugfixes * Fixed a bug in Django 4.2 where the deprecated ``DEFAULT_FILE_STORAGE`` and ``STATICFILES_STORAGE`` settings were not synced with ``STORAGES`` (:ticket:`34773`). + +* Fixed a regression in Django 4.2.2 that caused an unnecessary selection of a + non-nullable ``ManyToManyField`` without a natural key during serialization + (:ticket:`34779`). diff --git a/tests/serializers/models/base.py b/tests/serializers/models/base.py index e9f548ad3c6..c5a4a0f5802 100644 --- a/tests/serializers/models/base.py +++ b/tests/serializers/models/base.py @@ -60,7 +60,7 @@ class TopicManager(models.Manager): class Topic(models.Model): name = models.CharField(max_length=255) - category = models.ForeignKey(Category, models.CASCADE, null=True) + category = models.ForeignKey(Category, models.CASCADE) objects = TopicManager()